The present invention relates to a data collecting system, in which various values (physical or chemical quantities) measured by a plurality of measuring devices are collected or accumulated in one host apparatus.
In a factory, products are subjected to various inspections. An inspection line is provided in the factory to inspect the products. Measuring devices of various types are arranged along the inspection line. As the products are moved in the inspection line, their physical or chemical quantities are measured by means of the measuring devices. Pieces of data representing the physical or chemical quantities measured by the devices are collected in a host apparatus. The data collected in the host apparatus is used to calculate the quality and yield of the products.
There are various kinds of inspection performed on the products. One of them is the size-measuring of products. When the products have a complicated shape, ten or more dimensional values must be measured for each product. One person may use vernier calipers to measure all these dimensional values. Usually, however, several persons use vernier calipers or similar measuring devices, each person measuring a few dimensional values, This method is preferred since the work efficiency is higher, and the error rate is lower, than when each person measures all dimensional values of the product. Hence, many measuring devices of the same type are required in most cases.
The values measured by the measuring devices are collected in the host apparatus of a data collecting system. The data collection system comprises the measuring devices, cables, and relays. The measuring devices are connected to the relays by the cables, and the relays are coupled to the host computer provided within the host apparatus. Each relay has an input connector, to which a specific number is assigned. The number of the input connector is used as the identification (ID) number of the measuring device connected to the relay by the cable. The host computer can identify each measuring device with this ID number.
The host computer of the data collecting system contains a program defining what dimensional values should be measured of each product, and also in what order they should be measured. Several persons take their positions along the inspection line. The first person measures the first dimensional value of each product, by using his measuring device. The second person measures the second dimensional value of the product, and so forth. The values measured by these persons are automatically transmitted from the measuring devices to the host computer through the cables and the relays. The host computer identifies each measured dimensional value in accordance with the connector number of the relay through which this value has been transmitted, and also the time at which this value has been input to the host apparatus.
The data collecting system described above has some drawbacks, however. The cable connecting each measuring device to the relay coupled to the host computer may hinder the person using the device in his work, particularly when the measuring device is vernier calipers. In short, the cable may reduce the work efficiency. Further, the number of measuring devices which can be connected to one relay is limited. Hence, the more measuring devices, the more relays. An increase in the number of relays no doubt results in an increase in the size and cost of the data collection system. In order to eliminate this problem, one measuring device can be disconnected from an input connector of a relay after it has been used to measure a dimensional value, and another measuring device can then be connected to the same input connector. This disconnection/connection process is rather cumbersome and time-consuming. Not only will it decrease the work efficiency, but it is also likely to be erroneously performed.